20 for rare.....25 for medium-rare......but you have to factor in, or consider the shape and thickness depending on what cut of beef you are roasting and whether it has bones or not. Think Rib-Eye as opposed to a Strip Loin

I usually cook mine at 200 degrees until it gets to 120 degrees on the meat thermometer and then finish it at very high heat until it gets to 135. 375 seems to me like a high temperature to cook roast beef.

I found Giada's recipe for roast beef with Pasrley tomato sauce...and when I saw 40 mins @ 375 i got excited and went for it as an after work meal (i had always remembered roast beef taking a long while to cook...so when I saw 40 mins i thought that sounded fast..but went for it)

I guess I need to jump on the slow roasting bandwagon and save that puppy for a weekend when i have more time..

I always use top round (same as top sirloin?) but braising would ruin it. Simply, put a thick layer of salt and seasonings on top, put it in at high heat, turn down to 350 and cook 15 minutes per lb. This results in the old kind of deli style roast beef that drips blood, the way we like it here. I usually don't get smaller than 3 lbs though, 2.5 sounds sort of small if you like your meat on the rare side.

Sear the roast on all sides in a cast iron pan. Season with salt and pepper and put it on a rack in a roasting pan and place in a 200 degree oven. Slow cook until the interior temp is 110 degrees. Crank oven up to 500 and brush the roast with garlic butter. Put back in oven for 10-15 minutes more or enough time to brown all sides to your liking while attaining a finishing internal temp of 130.

The outside should be nicely caramelized goodness and the inside should be medium rare from edge to edge.

I've had really good luck with dry aging the roast for a few days in the fridge before cooking. It intensifies the flavor. I'll also second the slow roasting for most of the cooking time and just finishing it off in a hot oven.